The following information is provided to assist the reader in understanding technologies disclosed below and the environment in which such technologies may typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the technologies or the background thereof. The disclosure of all references cited herein are incorporated by reference.
A self-contained breathing apparatus (“SCBA”) is a device used to enable breathing in environments which are immediately dangerous to life and health (sometimes referred to as “IDLH” environments). For example, firefighters wear an SCBA when fighting a fire. The SCBA typically has a harness or carrier system including a backplate supporting an air tank which is connected to a facepiece, all of which are worn or carried by the user. The tank typically contains air or oxygen-containing breathing gas under high pressure (for example, 2200-5500 psi or 15,168 to 37921 kPa) and is connected to a first stage regulator which reduces the pressure to about 80-100 psi or 552 to 689 kPa. The SCBA usually has a second stage regulator that has an inlet valve which controls the flow of air for breathing between the air tank and the facepiece. Typically, the inlet valve controls the flow of air through the second state regulator in response to the respiration of the user. Such respiration-controlled regulator assemblies are disclosed, for example, in U.S. Pat. Nos. 4,821,767 and 5,016,627.
Under the 2002 edition of NFPA 1981 (Standard on Open Circuit Self-Contained Breathing Apparatus for Fire and Emergency Services), manufacturers must include a Rapid Intervention Crew/Universal Air Coupling (RIC/UAC), sometimes referred to herein as a universal air coupling or UAC in SCBAs to be in compliance for firefighting. The UAC allows a cylinder that is low on air to be “transfilled” from another, secondary cylinder regardless of the manufacturer thereof. After the transfilling process, each cylinder may, for example, have an equal amount of air. The UAC must be permanently fixed to the SCBA within four inches of the threads of the SCBA cylinder valve.